Subjective probability is one's personal belief that an event will occur, stated numerically. This probability is based on the experience or intuition of the individual; there is no basis on underlying data. There can be a large amount of personal bias built into the resulting estimates, to the extent that a statement of subjective probability is more likely to vary significantly from the actual outcome.

As an example of subjective probability, a football fan states that his favorite team has a 60% chance of winning the league championship this year.